Containers made of flexible materials, such as from thin sheets of plastics, offer distinct advantages over metallic cans, bottles and the like. For example, they are lighter, far less expensive to produce, and easier to discard. However, they have, to date, had their own problems and limitations. For example, being made of such thin and flexible materials they have not had the sturdiness of cans and glass or rigid plastic bottles nor the stability of such when filled and stood uprightly. To overcome this problem flexible material containers have been formed with reinforced bottoms or sides as shown in U.S. Pat. No. 5,135,464. For efficiency of manufacture such reinforcements have been formed by doubling of the layers of plastic film in selected locations along or adjacent to the container bottoms as they are manufactured from a continuous web. The doubled layers are fused by heat sealing. However, with such construction multiple layers of film are brought together at junctions wherein as many as six layers often meet and are fused. This has resulted in constructions that possess capillary leaks that can lead to degradation in characteristics of goods stored therein over time or the leakage of goods therefrom.
Another problem associated with such containers has been their lack of consistency of production. In their manufacture a continuous web of thin plastic material is drawn through a series of forming stations where the web is folded and refolded, cut and heat sealed in various locations. In doing so, the web is passed through sets of drive and idle rollers and over various guide bars. Quite naturally it has been difficult to control the thin, flexible web as it is intermittently pulled, twisted, pressed and heated with a degree of accuracy and consistency as to produce substantially identically constructed containers. This fact has also served to limit the minimal thickness of the web since the thinner the material the more difficult it is to control during manufacture.
Another problem associated with flexible containers has been their propensity to burst open or otherwise breach should they be dropped. This breaching of the container typically occurs along the junction of the seams wherein the sides of the dropped container bellow outwardly from each other thereby ripping the side seams open.
It thus is seen that there remains a need for flexible containers of improved construction and of methods of manufacturing containers made from very thin, flexible webs or sheets of material with improved accuracy and consistency of construction and yet which produce sturdy containers that are substantially free of capillary leaks and that are resistant to breaching. Accordingly, it is to the provision of such that the present invention is primarily directed.